1. Field of the Invention
The present invention relates to an ink jet printing apparatus, a data generation apparatus and a printed product. In particular, the present invention relates to an ink jet printing apparatus using printing properties enhancing liquid and colored inks, a data generation apparatus and a printed product.
2. Description of the Related Art
An ink jet printing method is a printing method for printing by causing small droplets of ink to splash and adhere to a printing medium such as paper. For this reason, when the ink adheres to the printing medium, a contour part may become unclear due to permeation of ink droplets into the printing medium particularly in the case where a printing medium such as plain paper is used. Moreover, a phenomenon of blurring on a boundary between different colors adjacent to each other (so-called color bleeding) may occur.
Against this background, there has been disclosed a method for applying an ink containing a dye having at least one carboxyl group after application of a solution containing polyvalent metal salt to a printing medium as the art of reducing color breeding by Japanese Patent Laid-Open No. Hei 5 (1993)-202328. Specifically, a solution (printing properties enhancing liquid) containing polyvalent metal ions and an ink containing a dye that can react with the ion come into contact with each other on a printing medium to form an insoluble substance. As a result, unclarity in the contour part is eliminated, and color bleeding is reduced. Furthermore, it is possible to obtain high-quality images in which going-through of a color material to a back surface of the printing medium is reduced (hereinafter also referred to as going-through resistance).
Moreover, there has been disclosed a technique of obtaining high-quality color images having high image density without color bleeding by using a combination of a black ink to be viscous or coagulated by reaction with salt and a color ink containing the salt by Japanese Patent Laid-Open No. Hei 6 (1994)-106735. In the above technique, two liquids which react with each other when mixed together are used as a set, and an image is formed on a printing medium by using such two liquids having different properties in image formation. Accordingly, clear images are obtained (an ink set using approximately achromatic liquids regardless of reaction will be hereinafter called a two-part liquid system). Besides the above, various techniques using two liquids have been disclosed by Japanese Patent Laid-Open Nos. Hei 3 (1991)-240557 and Hei 3 (1991)-240558.
With the two-part liquid system using such an ink set, unclarity in a contour part is eliminated. Moreover, in the case where a plurality of different color inks are used, high-quality images having excellent going-through resistance without color bleeding can be formed.
Specifically, in an image formation method using the two-part liquid system, polyvalent metal ions in a printing properties enhancing liquid react with a color material in an ink. For example, when the color material is a dye, the dye is coagulated. Moreover, when the color material is a pigment, the pigment is dispersed and destroyed. As a result, it is possible to achieve effects of eliminating unclarity in the contour part and of suppressing occurrence of color bleeding.
However, when the two-in-one liquid system is used, it is required to allow the two liquids, the printing properties enhancing liquid and the ink, to come into contact and react with each other on or in the printing medium. Thus, an amount of the liquids applied onto the printing medium may be increased compared with the case of a one-in-one liquid system using only an ink for image formation. As a result, in the case of the two-in-one liquid system, occurrence frequency of curling of printed paper is increased, and the curling occurs more frequency than in the case of the one-in-one liquid system.
To solve this problem, there has been disclosed a technique of suppressing curling by adding a heretofore known curling inhibitor to an ink by Japanese Patent Laid-Open No. Hei 6 (1994)-157955. For details, 1,3-diols, 1,3,5-triols, amino-1,3-diols or the like is added as the curling inhibitor into the ink. The above method can suppress occurrence of curling. However, a large amount of the curling inhibitor has to be added into the ink. This may result in deterioration in image quality of images to be obtained, the clogging of nozzles, apparatus reliability and the like.
As an alternative for the above configuration, there has been disclosed a method for applying a curling inhibitor for reducing curling onto a back surface of printing paper by use of a coating roller (Japanese Patent Application Laid-Open Publication No. Hei 8 (1996)-216384). The above document also discloses selective application of the curling inhibitor by use of a liquid ejection head having the width of a printing medium. To be more specific, this document discloses the application of the curling inhibitor by selecting its application region corresponding to an ink application region on a front surface.
However, in the method disclosed in JPA 8-216384 for applying the curling inhibitor for reducing curling onto the back surface of the printing paper by use of the coating roller, there arises a need to provide the curling inhibitor liquid and the coating roller only for suppression of curling. Moreover, consumption of the curling inhibitor liquid may be increased by application on the entire surface of a printing medium, and an apparatus size may be increased by providing the coating roller.
Meanwhile, by using the ejection head having the width of the printing medium to selectively apply the curling inhibitor liquid, the consumption of the curling inhibitor liquid can be suppressed. However, even in a configuration using an ejection head for the curling inhibitor liquid, a dedicated part for suppression of curling is to be provided after all. Thus, problems such as increases in the apparatus size and in cost still remain unsolved.